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The radiological safety assessment of high‐level radioactive waste (HLW) deep geological disposal facilities is essential for ensuring responsible and sustainable nuclear waste management. This study aims to develop a radionuclide transport model using the GoldSim code to simulate radionuclide release from spent nuclear fuel, facilitating the safety assessment of HLW deep geological disposal. Two types of reference South Korea's pressurized water reactor spent nuclear fuels (PWR SNFs), namely PLUS7 and ACE7, were utilized to calculate the radioactive inventory. Due to the absence of a high‐level waste disposal site in Korea, conservative input parameter values were adopted from the relevant literature for the conceptual modeling component. The radiological safety assessment indicated that the reference Korea's PWR SNFs did not exceed 1 mSv/year, even lower than South Korea's natural background rate (2.4 mSv/year). Both C‐14 and I‐129 were identified as the primary contributors to the total exposure dose compared to other radionuclides, and a sensitivity analysis was conducted for these radionuclides. The investigation into the influence of distribution coefficients (Kd) of C‐14 and I‐129 in the buffer and the host rock revealed that the radiological peak dose rate is more affected by the buffer than the host rock. Buffer sorption in the near field was found to significantly reduce the equivalent exposure dose. Overall, this study's findings can inform the establishment of conditions for deep geological disposal and provide quantitative analysis methods using GoldSim for the crucial long‐term safety evaluation of a high‐level waste repository. [ABSTRACT FROM AUTHOR]

A low- and intermediate-level radioactive waste repository contains various types of radionuclides and organic complexing agents. Their chemical interaction within the repository can lead to the formation of radionuclide-ligand complexes, influencing the limited retention behaviors of radionuclides. This study focuses on the sorption behavior of radionuclides on both engineered (concrete) and natural barriers (sedimentary rock and granite), as well as the prediction of sorption distribution coefficients (Kd) using support vector regression. Batch studies were conducted to determine the K d values for three radionuclides (99Tc, 137Cs, and 238U) under different conditions, including pH, temperature, and the presence of organic ligands (such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, and isosaccharinic acid). The K d values for 238U exhibited a sharp decrease with increasing concentrations of organic ligands. In contrast, the K d values for 99Tc showed only a slight reduction at higher organic ligand concentrations. Meanwhile, the K d values for 137Cs remained relatively unchanged, regardless of the type and initial concentration of organic ligands. This suggests a high level of retention for 137Cs in the rock samples. The support vector regression model with a radial basis kernel function proved effective in predicting the K d values under different experimental conditions. This enhancement in predicting accuracy contributes valuable insights into understanding the sorption processes involved in radionuclide behavior. Overall, this study advances our knowledge of radionuclide behavior on both engineered and natural barriers while providing a reliable prediction tool for estimating sorption distribution coefficients. [ABSTRACT FROM AUTHOR]

Microbial electrosynthesis (MES) has emerged as a sustainable energy platform capable of simultaneous wastewater treatment and valuable chemical production. The performance of MES, like other bioelectrochemical systems, largely depends on its electrode (cathode), providing the platform for microbial growth as well as electron transfer. However, most of the electrodes are expensive, and their nonrenewable characteristics, cost, and poisoning nature are major bottlenecks in MES commercialization. Thus, several efforts have been made to explore the potential of waste carbon-based electrodes to reduce carbon footprints as well as electrode manufacturing costs. In this study, the feasibility of using spent tea leaves (STL) and spent coffee grounds (SCG) as MES biocathode was tested. Different bioelectrochemical tests suggested improved MES performance with STL and SCG biocathode along with reduced electrode resistance and improved current density. A 1.5- and 2.0-fold increase in cyclic voltammetry (CV) current output was observed for SCG and STL, respectively, with substantial mediator peaks of high intensity indicating enhanced electrocatalytic activity. Enrichment of some fermentative and exoelectrogenic microbial classes such as Clostridia, Bacteroidia, and Deltaproteobacteria led to a 1.3- and 1.4-fold increase in butyrate production for SCG and STL cathode, respectively. These results demonstrate the potential of STL and SCG as MES cathode for improved energy and chemical production. [ABSTRACT FROM AUTHOR]